1. Field of the Invention
The present invention relates to a method and a device for removing slag, which is generated on a surface of molten metal in a metal furnace.
2. Description of the Related Art
When a metal material is liquidized in a liquidizing furnace by heating in a vacuum atmosphere so as to form a molten metal and cast into a mold for precise casing, slag is generated on a surface of the molten metal. Since it is difficult to remove the slag, the molten metal is cast in the mold with the slag, the slag affects the quality of the produced cast products. Particularly in producing precise cast products (for example, parts for air and space industry), any slag is not allowed to be contained. Thus, any contaminant of the slag significantly affects the yield of the cast products particularly in the precise cast products field.
Heretofore, when the molten metal is cast into the mold, slag is conventionally prevented from entering into the mold by the following methods: One method is to remove the slag by tilting the furnace to the other side of the mold for removing the slag before pouring the molten metal into the mold. Another method is to remove the slag by installing a filter at an entrance of the mold for filtering the slag.
However, even though the slag can be removed by tilting the furnace to the other side of the mold before pouring the hot melt into the mold, it is difficult to remove the slag perfectly. By installing a filter at entrance of the mold for filtering the slag, it is easy to remove a larger size of the slag, but it is difficult to remove a smaller size of the slag. If trying to remove the smaller size of the slag by the filter, it is required to make the filter finer, however when making the filter finer, it causes slower of flowing speed of the molten metal into the mold and generates bad products because of lack of the molten metal flowing into the mold. Further, the filter chips easily, and when chip of the filter is entered into the mold with hot melt, it generates bad products because of contaminants of filter chip.
Further, a method of removing slag, which is floating on a surface of the molten metal, in air atmosphere is known as Japanese laid-open patent publication No. H5-240588.